I just replaced a fan in a 90 Cherokee - only 2 wires - black is ground, white is hot. If they are reversed, the fan runs backwards. The fan cost me $5 at a wrecking yard. May be the simplest solution.
If it only has two leads and reversing them makes it run backwards, that would indicate a permanent magnet field.
On house wiring and things like that, white signifies neutral ...
As I stated, WHITE signifies the grounded conductor. For single phase/three wire, as commonly used in house wiring, the grounded conductor is the neutral but not so on all systems.
In Automotive, black usually signifies ground. Same for most electronics devices.
Make that battery powered electronic devices.
Decent parts houses carry all the variations of switches you'd need for a fan installation, ...
So does Radio Shack and most hardware stores.
... and they don't have to be mounted in J boxes. No, JC Penny does not carry them, neither does 7-11.
Now was that necessary?
Fortunately after the fan is installed on the YJ (that's a Jeep Taz,) you don't have to call the building department to to get it inspected to make sure you had a permit and did it to code.
Or was that?
Still, fires are so inconvenient.